Spin dynamics of field-induced spin density waves in bechgaard salts

Abstract

Theoretical results for spin response functions of field-induced spin density waves (FISDWs) in Bechgaard salts are summarized. The transverse spin susceptibility in a FISDW develops a pole near q = Q, describing a spin wave with dispersion ω 2 = ν F 2( q − Q) 2 + 2 δ 2 where δ is the quasi-particle energy gap. Furthermore the nuclear spin lattice relaxation rate diverges on both sides of the FISDW transition temperature T c like |T − T c| −1/2 due to three-dimensional spin fluctuations. On the other hand, the longitudinal spin susceptibility is given by χ 33(ω, q) = N 0ν F 2q 2((1 − U)ν F 2q 2 − ω 2) −1 for all temperatures independent of the FISDW transition, where N 0 is the density of states at the Fermi surface and U = UN 0 is the dimensionless Coulomb potential.